Electric switch having improved blade construction



United States Patent Inventor Russell E. Frink Pittsburgh, PennsylvaniaAppl. No. 790,088

Filed Jan. 9,1969

Patented Dec. 1, 1970 Assignee Westinghouse Electric CorporationPittsburgh, Pennsylvania a corporation of Pennsylvania ELECTRIC SWITCHHAVING IMPROVED BLADE CONSTRUCTION 7 Claims, 4 Drawing Figs.

U.S. Cl 200/48, 200/170 Int. Cl "01h 31/00 Field of Search 200/ l 70,

[56] References Cited UNITED STATES PATENTS 2,759,076 8/1956 CurtisZOO/170A 3,299,240 l/l967 Foti 200/l 66C Primary Examiner Robert K.Schaefer Assistant Examiner-H. J. Hohauser Attorneys-A. T. Stratton andClement L. McHale ABSTRACT: An electric switch comprising a switch blademovable between open and closed positions with respect to a relativelystationary contact means with a portion of said blade being formed fromaluminum and a portion of said blade being formed from an electricallyconducting material other than aluminum.

E 4? I93 4| W////////V//////// PATENTED DEC! 1970 SHEET 10F 2 PATENTEUum 19m 334474 2 SHEET 2 OF 2 INVENTOR Russell E. Frink ATTORNEY ELECTRICSWITCH HAVING IMPROVED BLADE CONSTRUCTION CROSS-REFERENCES TO RELATEDAPPLICATIONS Certain inventions disclosed in the present application arerelated to inventions disclosed and claimed in copending U.S. Pat.application Ser. No. 772,715 filed Nov. 1, 1968 which issued Mar. 10,1970 as U.S. Pat. No. 3,500,006 and Ser. No. 790,078 filed concurrentlyby E. W. Kuhn which are both assigned to the same assignee as thepresent application.

BACKGROUND OF THE INVENTION This invention relates to electric switchesand more particularly to a construction of the blades which form part ofsuch switches.

In certain types of outdoor high voltage electric switches, a problemarises in providing a switch construction in which as many of theelectrically conducting parts of the switch as possible are formed fromaluminum to obtain certain advantages such as a reduction in the weightof the parts of the switch which must be supported by the associatedinsulator supports. This problem arises because of the high resistanceoxide coating which forms on aluminum when it is exposed to atmosphericconditions or air and because of the galvanic corrosion which normallyresults when aluminum is structurally connected to a differentelectrically conducting material, such as copper or a copper alloy.Various constructions have been proposed in the disclosed in U.S. Pat.Nos. 3,206,568; 3,243,561; 3,299,240 and 3,388,225. These known switchstructures have been found to have certain disadvantages due todifficulties in manufacturing or when subjected to long continued use inservice.

SUMMARY OF THE INVENTION In accordance with the invention, an electricswitch includes an elongated switch blade or contact arm having one endmovable into and out of engagement with an associated relativelystationary contact means. The end of said switch blade which is movableinto engagement with the stationary contact means includes a portionwhich is substantially rectangular in cross section and which includes apair of relatively wider opposite planar surfaces interconnected by apair of relatively narrower opposite planar surfaces. A pair ofgenerally L-shaped electrically conducting contact members is secured tothe last-mentioned end of the blade for movement therewith to engage thestationary contact means. Each of the contact members includes arelatively longer planar surface which is disposed to engage one of thewider planar surfaces .of the last-mentioned end of the blade and arelatively shorter planar surface which is disposed to engage one of theadjacent narrower planar surfaces of said one end of the blade. In onepreferred embodiment, the blade including the end which engages thestationary contact means is formed from aluminum and the associatedcontact members on said one end of the blade are formed from copper or acopper alloy.

It is therefore an object of this invention to provide an electricswitch having an improved blade construction.

Another object of the invention is to provide an improved electricswitch construction including a movable switch blade which is formedpartially from aluminum and partially from an electrically conductingmaterial other than aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of the invention will beapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a partial view, in side elevation, of a disconnecting switchstructure embodying the principal features of the invention;

FIG. 2 is a top plan view of the switch structure shown in FIG. I;

FIG. 3 is an enlarged view, partly in end elevation and partly insection, of a portion of the switch structure shown in FIGS. 1 and 2;and

FIG. 4 is an enlarged view, partly in side elevation and partly insection, of the portion of the switch structure shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingsand FIGS. I and 2 in particular, there is shown a disconnecting switchassembly 10 which comprises three spaced insulator stacks 32, 34 and 36which are normally mounted upon a common base support (not shown) asdisclosed in detail in U.S. Pat. No. 3,194,905 which issued July 13,1965 to F. W. Jewell et al. and which is assigned to the same assigneeas the present application. Each of the insulator stacks 32, 34 and 36comprises a plurality of insulators which are preferably formed fromporcelain or a similar insulating material. The number of insulatorsrequired in each of the insulator stacks 32, 34 and 36 depends upon thevoltage of electrical system in which the disconnecting switch 10 isapplied. As illustrated, the insulator stacks 32 and 34 may be mountedupon fixed pedestals or spacers (not shown) which, in turn, may besecured to the top of the associated base which may be a metal channelin configuration. As described in the last-mentioned patent, theinsulator stack 36 is mounted upon a shaft (not shown), the lower end ofwhich is rotatably mounted in a bearing (not shown) which is secured tothe associated base. As indicated in FIG. 2, an operating lever or crankarm 37 may be secured to the shaft provided at the lower end of theinsulator stack 36 to rotate the insulator stack 36 with the crank arm37 being adapted for connection to any conventional means for operatingthe crank arm 37 to effect rotation ofthe associated shaft and theinsulator stack 36 about its own longitudinal axis.

In order to positively connect the crank arm 37 and the associatedrotatable insulator stack 36 to the balance of the operating mechanismof the disconnecting switch 10, as will be described hereinafter, ashaft 112 secured'to and extends upwardly from upper end of theinsulator stack 36 to thus form an extension of the shaft which isprovided at the lower end of the insulator stack 36. The shaft 112passes through an opening provided in the terminal end casting or member110 which is substantially alined with the axis of rotation of the shaft112 and the associated insulator stack 36 and has mounted at the upperend thereof a crank arm which is rotatable with the shaft 112 and whichextends generally at an angle or generally transversely with respect tothe axis of rotation of the shaft 112. In order to facilitate therotation of the shaft 112 inside the opening provided in the terminalend member 110, one or more sleeve bearings (not shown) may be disposedinside the opening provided in the terminal end member where desired. Itis to be noted that in a particular application, the crank arm 100 maybe formed integrally with the shaft 112.

As illustrated in FIGS. 3 and 4, the disconnecting switch 10 includes agenerally U-shaped relatively stationary contact assembly or break jawassembly 40 which is mounted on and secured to the top of the insulatorstack, 32. The stationary contact assembly 40 includes a plurality ofpairs of spaced contactjaws 43 which are mounted on and interconnectedby a generally U-shaped base member 41 which is forged or cast from anelectrically conducting material and which is secured to the top of theinsulator stack 32 by suitable means, such as the bolts 193. The basemember or terminal casting 41 is preferably formed from aluminum and insuch a construction, the contact jaws or members 43 are preferablyformed from copper or an alloy of copper in order toavoid the problemsassociated with the high resistance oxide coating that would result ifthe contactjaws 43 were also formed from aluminum and exposed to air oratmospheric conditions. In order to substantially eliminate the need foradditional or separate spring or biasing means to bias the contact jaws43 toward one another for gripping the free end of the associated switchblade 50 when the disconnecting switch is in a closed circuit condition,as shown n in FIGS. 1 and 2, the contact jaws 43 may be-formed fromasuitable electrically conducting material which combines relatively highelectrical conductivity with excellent spring or resilientcharacteristics, such as beryllium-copper; cadmium-chrome-copper,zirconiumcopper, phosphorus-bronze or the like. Where desired, separateresilient means, such as springs (not shown) may be provided toadditionally bias the contact jaws 43 toward one another. The contactstrips 172 maybe secured to the portions of thecontact jaws 43 which areengagedby. the associated switch blade 50 by suitable means, such asbrazing, and are preferably formed from silver or a silver alloy. Afterthe contact jaws 43 are bentto the desired shapes, as best shown in H6.3, and the contact strips 172 are brazed to the associated contact jaws43, the contact jaws 43 and the associated contact strips 172are'preferably provided with a heavy tin coating by hot dipping thecontact jaws 43 and the associated contact strips 172 in molten tin.

In order to secure the contact jaws43 to the associated base member 41with arelatively low electrical resistance joint between the assembledparts, the base member 41 includes accurately machined surfaces on theoutside of each of the sidewall portions of the base member 4l which areadapted to receive the generally U-shaped contact jaws 43 as best shownin FIG. 3. Prior to the assembly of the contact jaws 43 on the basemember the surfaces of the base member 41 which are adapted to engagethe outer portions of the contact jaws 43 are coated with a suitablegrease-type, petroleum base joint compound such as that which is soldunder the trade name No-Ox-ld, Grade A Special. Next,-the surfaces ofthe base member 41 to which the contact jaws 43 are to be secured arethoroughly abraded through the joint compound with a wire brush. Thepresence of the joint compound substantially preventsoxidationof thenewly exposed aluminum which results from the abrading of the contactsurfaces on the base member 41. The contact jaws 43 are then boltedfirmly to the base member by suitable means, such as the bolts 152 asshown in FIG. 3. t

As best shown in H05. 1 and.2, a terminal pad 42 which is adapted toreceive a terminal connecter may be formed integrally with or secured toone side ofthe base member or terminal casting 41. An upwardly extendingmember 44 may also be formed integrally with or secured to the otherside of the base member 41.to act as a'stop for the movement of theassociated switch blade 50 into engagement with the contact jaws 43. Itis to be noted that the stationary contact assembly closed circuitcondition, as shown in FIGS. 1 and 2, a movable switch blade 50 isprovided. The blade 50 is elongated in shape and includes a main bodyportion, 56 which, as illustrated, is generally tubular in configurationand which is preferably formed from a lightweight electricallyconducting material, such as aluminum. The blade 50 also includes an endportion or beavertail member 53 at its left or free end. The beavertailmember 53 is also preferably formed by suitable means, such as castingor forging, from aluminum to avoid any problems of galvanic corrosion;at the joint between the beavertail member 53 and the, main body portion56of the blade 50. The beavertail member 53 of the blade 50 includes aportion which is substantially rectangular in cross section, asindicated at 53A in FIG. 3. The beavertail portion 53A includes a pairof relatively wider opposite planar surfaces 53C and 53E which areinterconnected by a pair of relatively narrower opposite planar surfaces53B and 531), as best shown in FIG. 3. It is to be noted that thebeavertail member 53 is secured to the main body portion 56 of the blade50 for movement therewith by suitable means, such as welding, asindicated at 55 in H6. 4.

In order to avoid the problems which would otherwise result if thebeavertail member 53 were simply formed from aluminum and contact areaswere provided on the beavertail member 53 to engage the stationarycontact assembly 40 and such contact areas were subject to the formationof a high resistance oxide coating when exposed to air or atmosphericconditions,,a pair of generally. L-shaped electrically conductingcontact members'l82 and 184 are secured to the beavertail member 53 formovement therewith to engage the stationary contact assembly 40 when thedisconnecting switch 10 is -in the closed circuit condition shown inFlGS. l and 2. The contact members 182 and 184 are formed fromanelectrically conducting material other than aluminum such as extrudedcopper and may have secured thereto by suitable means, such as brazing,contact inserts 18 6 and 188, respectively, which are preferably formedfrom silver or a silver alloy. The contact member 182 includes arelatively longer planar surface 182A which engages the wider planarsurface 53C of the beavertail member 53 and a relatively shorter planarsurface 1828 which engages the adjacent narrower planar surface 53D ofsaid beavertail member. Similarly, the contact member 184 includes arelatively longer planar surface 184A which engages the other of thewider planar surfaces 53E of the beavertail member 53 and a relativelyshorterplanar surface 1848 which engages the other of the adjacentnarrower planar surfaces 53B of said beavertail member. it is also to benoted that the contact members 182 and 184 include the recessesindicated at 182C and 184C, respectively, in order to prevent thecontact members 182 and 184 from bearing against one another whenassembled on the beavertail member 53 and to permit the full force ofeach of the bolts 162 to be applied between the contact members 182 and184 and the beavertail member Prior to the assembly of the contactmembers 182 and 184 with the beavertail member 53 of the blade 50, thecontact members 182 and 184 are preferably provided with a heavy coatingof tin by hot dipping the contact members 182 and 184 and the associatedcontact inserts 186 and 188, respectively, in molten tin. ln addition,the planar surfaces 53B, 53C, 53D and 53B of the beavertail member 53which engage or make contact with the contact members 182 and 184 arecoated with a grease-type, petroleum base joint compound, such as thatpreviously mentioned, and then abraded through the compound with a wirebrush to expose unoxidized portions on the planar surfaces ofthealuminum beavertail member 53. The contact members 182 and 184 are thenfirmly secured to the beavertail member 53 by suitable means,

such as a plurality of bolts 162, which pass through substantiallyalined openings in the contact members 182 and 184 and the beavertailmember 53. [t is to be noted that when two electrically conducting partssuch as the contact members 182 and 184 and the associated beavertailmember 53 are bolted together, most of the electrical current whichpasses between the parts transfers in the areas immediately under theheads of the bolts. A plurality of such current transfer areas have beenprovided (two per bolt) in the disclosed construction and whereadditional current carrying capacity is required between the parts,additional bolts may be provided.

When the disconnecting switch 10 isto be applied at high transmissionvoltages, a corona shielding member 46 may be mounted at the left end ofthe beavertail member 53 of the blade 50. More specifically, the coronashielding member 46 may be generally hollow spherical in configurationand include a threaded portion which is adapted to screw into aninmaterial, such as aluminum.

In order to support the blade 50 for rotation about its own axis and forarcuate movement about an axis which extends generally perpendicular tothe axis of the blade 50, the right end of the main body portion 56 ofthe blade 50 may be secured to the left end of a generally tubular crankmember 60 for movement therewith, as described in detail in copendingU.S. Pat. application Ser. No. 772,715 filed Nov, 1, 1968 by Edmund W.Kuhn which is assigned to the same assignee as the present application.Where the main body portion 56 of the blade 50 is formed of aluminum,the crank member 60 is also preferably formed from aluminum to avoid theproblems associated with galvanic corrosion at the joint between therespective parts.

In order to support the crank member 60 and in turn the blade 50 forrotation about a common axis which extends longitudinally of the blade50, the disconnecting switch includes a hinge member 70 having agenerally tubular portion 79 on which the crank member 60 is rotatablysupported as described in the last-mentioned copending application. Inorder to limit axial movement of the blade 50 and the associated crankmember 60 with respect to the hinge member 70, an electricallyconducting shaft (not shown) may be secured to the inside of the crankmember 60 and include a threaded portion which engages an internallythreaded portion of the hinge member 70, as disclosed in detail in thelast- .mentioned copending application. An electrically conducting pathmay be provided between the crank member 60 and the hinge member 70 byone or more resilient, electrically conducting members (not shown)disposed between the'crank member 60 and the tubular portion 79 of thehinge member 70, as disclosed in the above-mentioned copendingapplication. It is to be noted that the electrically conducting shaft(not shown) which is disposed inside the crank member 60 and the hingemember 70 are both preferably formed from an electrically conductingmaterial other than aluminum, such as copper or a copper alloy, in orderto avoid the problems of galvanic corrosion between the relativelymovable shaft and the hinge member 70.

In order to support the hinge member 70 for rotation about an axis whichis generally transverse or perpendicular with respect to the axis of theblade 50 and to support the blade 50 which is assembled on the hingemember 70, asjust indicated, for arcuate movement or travel about saidaxis, the spaced arms 82 of the hinge support member 80 are disposed onopposite sides of the hinge member 70, as best shown in FIG. 2. As shownin FIG. 2, the hinge member 70 includes a pair of hinge portions whichproject generally perpendicular to the axis of the tubular portion 79 ofthe hinge member 70 with the hinge member 70 being pivotally supportedbetween the arms 82 of the hinge support frame 80 by electricallyconducting hinge pins or studs (not shown), as described in thelast-mentioned copending application. The hinge pins which support thehinge member 70 are preferably formed from copper or a copper alloy andan electrically conducting path may be provided between the hinge pinsand the hinge member 70 by one or more resilient electrically conductingmembers (not shown) which may be disposed inside the generally tubularhinge portions of the hinge member 70 to engage both the hinge member 70and the hinge pins which are secured to the arms 82 ofthe hinge supportframe 80.

In order to provide an electrically conducting path between the hingesupport member 80 which is preferably formed from aluminum in order toreduce the weight of the electrically conducting parts of thedisconnecting switch 10 and the terminal end casting or member 110, thegenerally tubular electrically conducting member 86 structurallyconnects the hinge support member 80 and the terminal end member 110.The electrically conducting member 86 is preferably formed fromaluminum. The hinge support member 80 includes a flange portion 84having an opening therein which is adapted to receive the left end ofthe electrically conducting member 86 with the left end of theconducting member 86 being secured to the flange portion 84 by suitablemeans, such as welding.

Similarly, the terminal end member 110 also includes a flange portion114 having an opening therein which is adapted to receive the other endof the conducting member 86 with the right end of the conductingmember86 being secured to the flange portion 114 by suitable means, suchas welding. The electrically conducting member 86 may also serve as ahousing for a counter balancing mechanism or means which is described indetail in U.S. Pat. No. 3,074,474 which issued Feb. 26, 1963 to E. F.Beach et al. and which is assigned to the assignee as the presentapplication. The terminal end member 110 is also preferably formed fromaluminum in order to avoid the problems of galvanic corrosion at thejoint between the conducting member 86 and the portion 114 of theterminal end member 110.

When the disconnecting switch 10 is in the closed-circuit conditionshown in FIGS. 1 and 2, an electrically conducting path extends from theterminal path 42 at the left end of the disconnecting switch to theterminal pad 116 at the right end of the disconnecting switch 10 throughthe base member 41 and the contactjaws 43 ofthe stationary contactassembly 40, the contact members 182 and 184 on the beavertail member ofthe blade 50, the beavertail member 53, the main body portion 56 of theblade 50, the crank member 60, the shaft inside the crank member 60, theelectrically conducting members inside the crank member 60, the hingemember 70, the electrically conducting members inside the hinge member70, the electrically conducting hinge pins associated with the hingemember 70, the hinge support member 80, the electrically conductingmember 86, and the terminal end member 110 to the terminal pad 116.

In order to operatively connect or mechanically couple the crank arm 100which is mounted on or formed integrally with the shaft 112 which issecured to the top of the rotatable insulator stack 36 and the crankmember 60 in order to permit the movement of the blade 50 during openingand closing operations ofthe disconnecting switch 10, the disconnectingswitch 10 includes the operating link 90 which is pivotally connected tothe crank member 60, the slip joint 92 and the universal joint 120 whichoperatively connects the slip joint 92 to the crank arm 100.

More specifically, the crank arm includes a clevis portion whichcomprises the spaced arms 101 at the upper end thereof, as best shown inFIG. 1. As just mentioned, the crank arm 100 is operatively connected tothe operating link 90 by the universaljoint structure and the slip jointstructure 92. The universal joint structure 120 comprises a trunnionmember 102 which is pivotally supported in substantially alined openingsprovided in the spaced arms 101 of the crank arm 100 by a pair of pivotpins 103 which are secured to the trunnion member 102 for movementtherewith. The universal joint structure 120 additionally includes aclevis member 93 which is pivotally connected to the trunnion member 102by the pivot pin 104 for rotation about an axis which is generallyperpendicular to the other axis of rotation of the trunnion member 102.The clevis member 93 includes a partially threaded extension whichpasses into a bore provided in the right end of the operating link 90and has disposed thereon an adjusting nut 99 which forms part of theslipjoint structure 92, as described in detail in U.S. Pat. No.3,194,905 previously mentioned. As disclosed in detail in the U.S. Pat.just mentioned, the slip joint 92 permits limited relative movementbetween the operating link 90 and the clevis member 93 and includes aspring (not shown) which prevents bouncing of the blade 50 duringclosing operations. The operating link 90 which is of the forked type ispivotally connected to the crank portion 66 of the crank member 60 bythe pivot pin 67 which passes through an opening provided by the crankportion 66 of the crank member 60.

In the operation of the disconnecting switch 10, as described in greaterdetail in the last-mentioned patent, it is assumed initially that theblade 50 is in the closed position as shown in FIGS. 1 and 2 with themovable contact members 182 and 184 in engagement with the contact jaws43 of the stationary contact assembly and'the beavertail member 53 ofthe blade 50 in engagement with the blade stop 44. Under theseconditions, the operating mechanism of the disconnecting switch 10whichincludes the operating link90, the slip joint structure 92, theuniversal jointstructure 120 and the ing of the disconnecting switch 10to thereby actuate the blade 50 from the closed position shown in FIG. 1toan open position in which the blade 50 is angular ly displaced fromthe closed position by approximately 90 in a clockwise direction aboutthe axis defined by the hinge pins which support the hinge member 70.During an opening operation of the disconnecting switch 10, the slipjoint structure 92 effectively shortens the, length of the operatinglink 90 as thecrank arm 100 starts to rotate in a counterclockwisedirection about its own I axis of rotation to permit thetoggle-mechanism which in- ;cludes the operating link 90 and thecrankarm 100 to pass -through the dead center position. As the crank arm 100rotates further toward the undertoggle position from the dead centerposition, the slip joint 92 effectively lengthens the operating link 90to thereby eliminate any longitudinal pull on the operating link 90 butto. transmit a force from the crank arm 100 to the operating link 90through the clevis member 93 which provides a lateral force on'the crankmember 60 to rotate the blade 50 about its own axis to. effect adisengagementof theblade 50 from the contact jaws of the stationarycontact assembly 40; Continued counterclockwise movement of the crankarm100 provides a longitudinal pull on the operating link 90since thelengthening of the operating link 90 is limited by the slip jointstructure 92 and a force is therefore transmitted to the crank member 60to actuate arcuate movement of the blade 50 along with the hinge member70 in a counterclockwise direction about the axis defined by the hingepins which support the hinge member 70 until the blade gle position, theblade 50 is rotated in a counterclockwise direction from the openposition until the blade 50 and, more specifically, the left end of theblade 50 is actuated to a position between the contact jaws 43 and thebeavertail member 53 of the blade 50 rests upon the blade stop 44.Further, rotation of the crank arm 100 effects movement of the togglelinkage which includes the operating link 90 and the crankarm 100through the dead center position to the overtoggle position to therebyextend the slip joint structure 92 and to rotate the left end of theblade 50 into full engagement with the contact jaws 43 of the stationarycontact assembly 40, while the blade itself rests on the blade stop 44.In summary, the operating mechanism of the'disconnecting switch 10separates the rotary movement of the blade 50 about its own axis whichis necessary to either disengage or cause the left end of the blade, 50,to fully engage the stationary contact assembly 40 and the generallyarcuate movement of the blade 50 between the open and closed positionsjust described. i

It is to be understood that the teachings of the invention may beapplied to a disconnecting switch strut structure in which only the mainbody portion 56,.the beavertail member 53 and the crank member 60 areformed from aluminum while the balance of the electrically conductingparts of the disconnecting switch are formed from an electricallyconducting material other than aluminum, such as copper or a copperalby. In such a construction it is to be understood that the stationarycontact assembly may be formed with the contact jaws and the associatedbase member combined in a unitary member which is formed from a suitableelectrically conductt ing material which combines relatively highelectrical conductivity with excellent spring or resilientcharacteristics such as 'zirconium-copper or phosphorus-bronze, asdescribed in detail in US. Pat. No. 3,079,474 previously mentioned.

The apparatus embodying the teachings of this invention have severaladvantages. For example, a switch construction is disclosed including animproved blade structure which is uniquely adapted to the use ofaluminum in the main body portion and in the beavertail member whileproviding reliable joints between the contact members at the free end ofthe blade and the associated beavertail member. In addition, the movablecontact members disposed on the associated blade in the switchconstruction disclosed are easily replaceable, as required, in longcontinued service and the blade construction is relatively easy tomanufacture. A further advantage of the disclosed switch construction isthat current transfer is accomplished between the movable blade and theassociated contact jaws between relatively movable parts which areformed from an electrically conducting material other than aluminum,such as copper or a copper alloy, with joints between copper andaluminum parts where required being accomplished through the relativelyreliable bolted joints describedwhich have been proved dependable inlong continued service by past experience. Finally, the disclosed switchconstruction has the advantage that it does not depend upon the platingof aluminum parts which may separate from the aluminum when exposed tothe weather or atmospheric conditions during long continued use inservice.

Since numerous changes may be made in the above described apparatus anddifferent embodiments of the invention may be made without departingfrom the spirit and scope of the invention, it is intended that all thematter contained in the foregoing description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

Iclaim:

l. A disconnecting switch comprising a relatively stationary contactmeans, an elongated switch blade having one end movable between engagedand disengaged positions with respect to said stationary contact means,said one end including an electrically conducting portion which issubstantially rectangular in cross section and includes a pair ofrelatively wider opposite planar surfaces interconnected by a pair ofrelatively narrower opposite planar surfaces, a pair of generallyL-shaped electrically conducting contact members secured to said one endof said blade for movement therewith to engage said stationary contactmeans in the engaged position of said blade, each of said contactmembers including a first portion having a relatively longer planarsurface which engages one of the wider planarsurfaces of said one end ofsaid blade and a second portion having a relatively shorter planarsurface which engages one of the adjacent narrow I planar surfaces ofsaid one end of said blade, said second pertions only of said contactmembers being disposed to engage said stationary contact means in theengaged position of said blade.

2. The combination as claimed in claim 1 wherein said blade includingsaid one end is formed from aluminum and said pair of generally L-shapedelectrically conducting contact members is formed from-copper.

3. The combination as claimed in claim 1 wherein said blade includingsaid one end is formed from aluminunuand said pair of generally L-shapedelectrically conducting contact members is formed from an alloyincluding copper, said first por tions of said contact members eachincluding a recess adjacent to'the second portion of the other contactmember to prevent said contact members from bearing against one anotherwhen said contact members are secured to said blade.

4. The combination as claimed in claim 1 wherein said stationary contactmeans includes a plurality of pairs of spaced 6. The combination asclaimed in claim 4 wherein said pairs of spaced contact jaws are mountedon a generally U-shaped base member formed from an electricallyconducting material.

7. The combination as claimed in claim 5 wherein said pairs of contactjaws are mounted on a generally U-shaped base member formed fromaluminum.

